The tail of a potent Pacific storm is dropping snow across the San Diego County mountains and rain virtually everywhere else on what is expected to be the final day of nearly a week of cool, stormy weather.

The National Weather Service predicted up to 8 inches of snow would fall in the mountains and as much as 6 inches in Julian. There could be up to 2 inches at the 2,500 foot level, forecasters said.

The system also was expected to drop a quarter-inch of rain at and near the coast, and twice that across inland valleys and foothills, adding to the fall and winter bounty.

The weather service slashed snow and precipitation totals before dawn Tuesday after reviewing the latest computer models.

San Diego International Airport has received 8.89 inches of precipitation since the rainy season began on October 1. That’s 3.52 inches above average. The latest system will push the airport close to its annual average of 10.32 inches, forecaster said.

“We’re not expecting flooding because the rain will be like it was Monday — off and on, showery,” said Joe Cordero, a weather service forecaster.

Drivers around the region were finding slow speeds during Tuesday’s morning commute as rain continued to fall. The California Highway Patrol reported a “mini rock slide” blocking westbound lanes of state Route 76 at La Jolla Road near Rincon around 8 a.m.

A winter storm warning will be in effect for the county’s inland valleys and mountains through 5 a.m. on Wednesday. And it will be unseasonably cold everywhere. San Diego’s daytime high might not surpass 56.

John Gibbins / San Diego Union-Tribune

A cold wind was blowing at the top of Mount Laguna early Tuesday, where snow was falling. Forecasters expect up to 8 inches to fall in some areas.

A cold wind was blowing at the top of Mount Laguna early Tuesday, where snow was falling. Forecasters expect up to 8 inches to fall in some areas. (John Gibbins / San Diego Union-Tribune)

Motorists heading to Mount Laguna reported seeing a dusting of snow at the 5,200-foot level shortly after 8 a.m. Signs advised drivers to use snow chains but little snow had accumulated yet. Patches of ice were spotted on Sunrise Highway near the top.

Forecasters also say the winds could gust 30 mph to 40 mph in the mountains and along parts of eastern Interstate 8, making driving hazardous.

Heavy snow also was expected in the Sierra Nevada, which will eventually feed water to the state’s big reservoirs.